BPS (Black photo spacer) technology is a technology that combines two processes of BM (black matrix) and PS (gap control) into one process of LCD (Liquid Crystal Display) technology. The technology can perform a BPS process on the color filter substrate side or the array substrate side. Performing a BPS process on the array substrate side, and then use a COA (Color on Array, integrating the color filter substrate with the array substrate) technology to integrate the array substrate and the color film into a box, and the corresponding color filter substrate side has only one layer of front ITO (indium tin oxide) electrode layer, and there is no remaining film pattern. This design can be used in situations where the flat display and the curved display are shared.
Whether the BPS process is prepared on the side of the array substrate or the side of the color filter substrate, the peripheral shading is achieved by the BPS material layer. Since there is no color resist, it is impossible to prepare a color barrier wall to block the flow of the sealant and PI (polyimide). Therefore, under BPS technology, the sealant and PI process need to be strictly controlled, and often there will be cases where the specification is exceeded.
FIG. 1 is a design of a sealant and a retaining wall of a liquid crystal display panel corresponding to the prior art, wherein 11′ is a glass substrate, 12′ is a gate metal, 13′ is a source-drain metal, and 14′ is a gate insulation layer, 2′ is the passivation layer, 3′ is the sealant, 4 and 5′ are the alignment layer (for the polyimide material), 6′ is the ITO electrode layer, 7′ is the black matrix layer, and 8′ is the color filter substrate. 9′ is a retaining wall, and 11′, 12′, 13′, and 14′ form an array substrate. Since the BM process and the PS process are separated, and the planarization layer is not used, the color film substrate side can use the color resist to form a retaining wall between the sealant and the alignment layer, and the color resist is used as the alignment layer and on the side of the array substrate, the color resist is used to form a retaining wall between the alignment layer and the sealant.
FIG. 2 is a schematic view of a liquid crystal display panel prepared by using a BPS technology, wherein 11′ is a glass substrate, 12′ is a gate metal, 13′ is a source-drain metal, 14′ is a gate insulation layer, and 2′ is a passivation layer. 3′ is the sealant, 4 and 5′ are the alignment layers, 6′ is the ITO electrode layer, 8′ is the color filter substrate, 10′ is the planarization layer, 20′ is the BPS material layer, 11′, 12′, 13′ and 14′ form an array substrate. Since there is no patterned film layer on the side of the color filter substrate, there is no design for the retaining wall. The BPS material layer on the side of the array substrate functions as a light-shielding effect, so that a convex retaining wall cannot be made, and even if the color resist is used as a retaining wall, the planarization layer and the BPS material layer are both organic layers, and both are very thick, so that the protrusion of the color-resist will be flattened by two layers of the organic layers, which will not function as a retaining wall.